Rheostat



Patented May 8, 1928.

UNITED STATES PATENT OFFICE.

JOSEPH B. EDWARDS, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SWITCH BOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIVS, A COREORATION OF ILLINOIS.

RHEOSTAT.

Application filed March 12, 1924. Serial No. 698,645.

My invention relates to rheostats used in connection with) an electric circuit for varying the resistance therein and more particularly for use in controlling the Current flow through the filament of an audion or electron tube; and an object of my invention is to provide a rheostat which is simple in construction and operation but very durable and efficient.

A feature of my invention is the provision of an improved helically wound resistance unit supported between a pair of disk meinbers which when clamped together secure the resistance unit in position against movement relative to the disks, the disks and resistance unit as a. whole forming a .compact and efiicient rotatable unit.

Another feature of iny invention is the provision of an arcuate shaped groove for each disk positioned at the peripheral edge of the inside face of each disk, the arcuate surface of each groove being corrugated and in which the convolutions of the resistance unit rest when the same is clamped between the two disks to secure the resistance unit as a whole in the annular channel formed by the arcuate grooves against displacement or movement.

The above features, as well as others, will be more ]:articularly pointed out in the ensuing specification and for a-more complete understanding of the rheostat of my invention reference may be had to the accompanying drawing in which like reference characters in the several views denote like parts7 and in which:

Fig. 1 is a front view of the rheostat of my inventio'n illustrating the same in its normal or off position;

Fioj. 2 is a left side view of Fig. 1;

Fig. 3 is a sectional view along the line 3-3 of Fig. 1;

Fig. L1 is a back plan view of the rheostat of. my invention; v

Fig. 5 is a view of one of the disks of the rotatable .element Clearly illustrating the arcuate shaped corrugated groove, and

Fig. 6 is a partial enlarged sectional view of the disks illustrating the helical resistance unit clamped in position with its convolutions resting in the corrugations.

Referring now more in detail to my invention as illustrated in the accompanying drawing the rheostat of my invention comprises a helically wound resistance unit 2 of a plurality of convolutions 3, constructed of suitable resistance material and of a predetermined resistance. The rotatable element R which supports the resistance unit 2 comprises a pair of disks 4 and 5 moulded of suitable insulation material such as bakelite. The inside faces 6 and 7 of the disks 4: and 5 are each provided with an annular arcuate groove 9 positioned at the peripheral edge of the disks 4 and 5. The disks L1 and 5 are assembled to form the rotatable element R by placing the inside faces 6 and 7 of the disks L1 and 5 together in match relation "ith each other by means of a sleeve member 10 which extends through aligned central orifices 11 of the disks 4 and 5. The sleeve 10 is provided with an intermediate reduced portion 15 and a. further reduced portion 16, the portion 15 of the sleeve 10 extending through the central orifices 11 of the disks 1 and 5 with the reduced end portion 16 protruding forward of the disk 4-. The interinediate reduced portion 15 of the sleeve 10 'protrudes slightly beyond the face of the disk 11 and a washer 17 is slipped over this protruding portion which is then npset by suitable means to secure the disks 11 and 5 together and prevent the sleeve 10 from turning in the orifices 11 in the disks st and 5. A plate 18 provided with a central orifice is slipped over the sleeve 10 and rests between the said sleeve 10 and the disk 5 for purposes as will presently be described. The arcuate grooves 9 of the disks '-1 and 5 form when the said disks are assembled as just describech an annular circular channel 19 which contains the helical resistance unit. 2 which is placed therein during` the assemblv of the disks 11 and 5. The annular grooves 9 are provided with corrugations 20 in which the convolutions 3 of the resistance 2 rest and screws 21 which pass through orifices 22 in the disk 5 have screw threaded engageinent with aligned tapped orifices 23 in the disk L1 to additionally clamp the disks 1 and 5 together to prevent tnrning of one disk relative to the other on the sleeve 10 and also clamp the resistance unit in the corrugated channel 19 formed by the arcuate grooves 9 for purposes as will presently be described. The end 21 of the resistance unit 2 passes through a suitable orifioe 25 in the disk 11 and is bent over to secure it in position therein and the end 26 of the unit 2 extends through a suitable orifice in the disk 5 and an orilice-27 in the plate 18 to connect the end 26 of. tlie unit 2 with the sleeve which is in turn conductively connected with the terminal 39. An .insulatiiig inemben 28 is also? clainped', in the channel' 19' and separat'es the respective ends of the 'resistance unit 2 and also is engaged'by the v-Jipolf;`

29 and 30 associated with the resistance unit 2 when the unit R which supports thelrcf.

i "'ince unit 2 isrin its normal position.V

i ne wipers- 29 and 30` are provided 'tor engaging the helical resistance unit 2and are separat'ed by means of a suitable terminal blocl-z t3i. A- pair of mounting legs 32 and are provided between which the tern'iinal''V block 31 andwvipers v29 andl30 are claniped by means of 'a suitable claniping screw '34. The terminal blot and wipers-.29tand 3 are suitablypinsulated from the mounting legs 32 and 33 by means of suitable insulation strips 35, and the clamping screws 3d which pass through suitable orifices in the mount-ing legs 32 and '33 terminal block ,31

and wipers 23 and 29 and insulation strips have scre: threaded engagement with and 36' by and through the central orifice 47' in" thesleeve 10, through orifice in plate IS--and through the-orifice Li3 in the leg 33, :and a set screw -Q having-screw threadedengagementl withthe-tapped oritice 50in thel'sleeve 10Ven-V ganz-es the sha'it to secure the 'unit a whole to the shai't 43') so that when the'actuating li'nob 51 which secured to the end of Vthe shaft 45 in any suitable inanner is turned the shatt i'which rotates'in the bearing orifices ati and LH in the legs 32 and 33 and it's supported unit R rotate as a wholeto place the convolution 3'of the resistance unit 2 in engagement with the wiper ends 29' and 30' to include av certain amount of resistance in the Operating` circuit in which my rhe'ostat is be-v ing used and 'when the rotata-ble unit R is rotated hack to its normal position the insulation separator 28 again engages the wiper end's 29' and 30'.

:As previously described the convolutions 3 of the resistance unit 2 when the said unit is parti'ally encompassed by the channeli19 rest in 'tiie corrugations in the groove 9' when thedisks Li and 5 are'securedtogether as before described to clanip the resistance unit 2 proper spa'ced' 'relation with their adj Su-itable terminals 38 and 39 areV in position so that as the Aunit R is rotated to place its supported nnitv 2 in Leng-agement with the wipers 29 and 30 the individual convolutions 3 will atall times i'emain inrtheir I "i'Ce'nt' convolutions and also' pre'ventI the resistance unit 2 as a whole from crceping iii the channel 1-9.

z The set, screwfi9 ,prevents removal oi' the shatt 45 and to maintain the rotatable unit in an ofv its adjustedpositions I providea dislied or: springiwasher 55 which whencinserted'between the end of the slee'veilO and' the leg -producesa trictional' -efi'ect bc'- tween the end' ot' the sleeve 10V and the/Washer 55 to hold the rotatable-unit- R iiiany of its'adjusted .positions 'I provide a -stop pin i 56- which is secured tolthe leg 32 :and a pin 57 secured to the rotatable unit R in any suitable inannei" engages the pinV fi'in its oii' position and .its extreme od normal position to liniit the rotation of'the unit R inits'oit' and extreme on positions.

In ig. 2 I illustratefthe rheostat mounted upon a'panel (SO-shown in dottedflines by means ot' a screw 61 which extends through' a suitable orifice in the panel (SO-and has screw Vthreaded engagement with a suitable tapped oriiice 62 in the leg -Vhile I have descri'bed -aipreiierred enibodiinent ot' niyY inventiom'it is to -be understood' that I do not'wish to'be limited to' the' eziact structure as shown andl de'scribed, as changesand modifications will readlly sugge-st'themsel'ves and I' therefore'aim to cover.

all such changes and 'inodifications as conie within the spirit and scope of the-appended' and means 'for prei'enting the -excessi've ro-` tation of said shaft, a resistance 'element' forined' of spirally woundv coii'\;olu-t-ioiis of 'conductiiig material, a pair of disks secured together to form a unit, a semi-circular cutaway portion in the inner portion othe peripheral elge of each of said diskssaid cutaway portions .forming a groove; substantially circular in shape, tor supporting and partially encoinpassing said resistance element7 depressions slantingly lformed in' the face of 'said cut-away portions vof a size to receive the Vconvolutions of-said resistance element, saiddepressions in one of' saiddi'sks adapted 'to coope'rate withi'the depressions in the' other of said disks to form continuous depressions each adapted Vto receive a single convolution of the said'resistancezelement to support the same `and `prevent it from creeping insaid groove, and a pair of wipers in op'erativerelation'with'said resistance element, both of said pair of wipers being;` adapted to sinmltaneously enga'ge the same convolution of the resistance element.

2. In a device of the Character descriloed including a pair ot members adapted to form U-shaped supporting means for a Wiper element, a rotatable shaft7 and means tor preventing` the eXcessive rotation of said shaft9 a resistance element comprising a plurality of convolntions of conducting material, said wiper element comprising` a pair ot Wipers adapted to simnltaneonsly engage the same convolutions ot said ref tance element, a pair of disks adaitcd to bo secured together to 'form a unitary structure by means including' a slceve member having its ends nptnrned to engag'e the out-side taces ot the disks and adapted to he atlixed to the said rotatalile shait't Whereby said disks are rotatahl)T secured on said shat't, a semi-circnlar cut-away portion in the inner port-ion ot the peripheral edge ot' each of said disks` said cut-away portions torming` a groove substantiallj.7 eircnlar in shape adapted to receive said resistance element and support and partiallvv encompass the same` means located near the pcriphery ot said dislrs adapted to engag'e said dislts to prevent movement of said disks relative to each other and to clamp said resistance element in said groove against displacement, depressions slantingly formed in the face of said cut-away portions of a size to receive the convolutions ot saidresistance element, said depressions in one ot said disks adapted to cooperate with the depressions of the other of said disks when the same are clamped together to form cont-innous depressions each adapted to receive a single convohitiorl ot the said resistance element to support the same and prevent it from creeping in said groove.

Signed 'o v me at Chicago, in the county of Cool: and State ot Illinois, this 10th day of March, 1924;.

JOSEPH B. EDTNARDS. 

